Quadratic equation

A quadratic equation is an equation in one variable that can be written in the standard form a times x squared, plus b times x, plus c, equal to zero, where a, b and c are known coefficients and a is not zero. The values of the variable that satisfy the equation are called its solutions, roots or zeros, and a quadratic equation has at most two of them, real or complex, counted with multiplicity. The quadratic formula expresses these solutions directly in terms of the coefficients a, b and c, and can be derived by a technique called completing the square. Solutions to problems that amount to quadratic equations were known as early as 2000 BC, and because the equation involves only non-negative integer powers of the variable, it is classified as a second-degree polynomial equation. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/